Bleeding from an exposed sternal end which was created by a median sternotomy incision results in blood being shed into the pericardium and pleural cavity. This bleeding is from both the cortical and medullary bone of both sections. Cortical bleeding can be controlled with the use of a diathermy device, however, bleeding from the medullary bone is more difficult to control.
Blood in the pericardium and pleural cavity obstructs visibility during surgical procedures. This blood is either returned to the heart lung machine via a cardiotomy return sucker or collected with a cell-saver unit. However, blood which has come into contact with the pericardial or pleural surfaces and is returned to the circulation via a cardiotomy return sucker will elicit a detrimental inflammatory response to the patient. Blood returned to the circulation via the cell-saver circuit will result in loss of valuable dotting factors and platelets.
Bleeding from the sternum during the operation and in particular at the completion of the procedure makes it more difficult to determine if there are significant other bleeding sources present within the mediastinum or pericardium. The attribution of mediastinal and pericardial blood at the completion of the operation to bleeding from the sternum is a common cause for missed surgical bleeding sites. This results in an increased incidence of reoperation for bleeding. This in turn is associated with an increased sternal wound infection risk.
Also, ongoing blood loss from the sternum post-operatively (once the patient is in the intensive care unit) makes it difficult to differentiate sternal bleeding from significant mediastinal bleeding sites. The above problems contribute to a higher blood transfusion requirement.
Furthermore, sternal retractors placed directly in contact with the sternum can lead to sternal fractures. As the retractor is opened, the distribution of force is usually at the point of contact of 2 to 3 blades on either side rather than being distributed over the entire length of the sternum more evenly, leading to concentrated loading and fractures.
Previous proposals to deal with bleeding from the sternal medullary bone include using bone wax to cover the exposed end and the application of topical haemostatic agents or absorbable haemostats.
Bone wax can be ineffective and the introduction of a permanent foreign body into the sternal medullar is undesirable. In this regard, surgeons can be reluctant to place a permanent foreign body into the sternal medullar due to potential risk of increasing infection rate or making infection more difficult to treat if it occurs. There is also some evidence to suggest that bone wax inhibits osseous fusion and promotes infections.
Furthermore, inserting bone wax into the sternal medullar in elderly patients with soft sternal medullar is extremely ineffective in improving sternal haemostasis and elderly patients make up a large proportion of patients undergoing cardiac surgery.
Topical haemostatic agents or absorbable haemostats can be difficult and cumbersome to apply, messy and ineffective in achieving sternal haemostasis.
It has been previously proposed to provide a cover for the exposed sternal end. One example is shown in U.S. Patent Application No. 2008/0215054 (Wright). This document discloses a U-shaped device comprising an end wall and opposed walls which surround the upper and lower surfaces of the sternum. The device is formed from a biocompatible plastic, hard elastomer or metal such as stainless steel, aluminium, titanium or other suitable metal. As the device is rigid, it is ineffective at forming a tight seal against the exposed sternal end of a patient whose cut sternum does not match the configuration of the device.
One problem with previous proposals is that the sternums of individual patients are differently sized and shaped and this makes it difficult to provide a solution which is adaptable for different patients. In this regard, the length, width and curvature of respective sternums can vary significantly from one patient to the next.
Previous proposals for stemming bleeding from an exposed end of a severed sternum have not adequately accounted for sternum size variations and it is not practical to manufacture covers in the vast number of sizes that would be required.
Embodiments of the invention seek to solve, or at least ameliorate, one or more disadvantages of previous methods and apparatuses for stemming bleeding from an exposed end of a severed sternum.